Formulation of PID control for DC-DC converters based on capacitor current: A geometric context

Santanu Kapat, Philip T. Krein

Research output: Contribution to journalArticlepeer-review

Abstract

The output voltage derivative term associated with a PID controller injects significant noise in a dc-dc converter. This is mainly due to the parasitic resistance and inductance of the output capacitor. Particularly, during a large-signal transient, noise injection significantly degrades phase margin. Although noise characteristics can be improved by reducing the cutoff frequency of the low-pass filter associated with the voltage derivative, this degrades the closed-loop bandwidth. A formulation of a PID controller is introduced to replace the output voltage derivative with information about the capacitor current, thus reducing noise injection. It is shown that this formulation preserves the fundamental principle of a PID controller and incorporates a load current feedforward, as well as inductor current dynamics. This can be helpful to further improve bandwidth and phase margin. The proposed method is shown to be equivalent to a voltage-mode-controlled buck converter and a current-mode-controlled boost converter with a PID controller in the voltage feedback loop. A buck converter prototype is tested, and the proposed algorithm is implemented using a field-programmable gate array.

Original languageEnglish (US)
Article number5982421
Pages (from-to)1424-1432
Number of pages9
JournalIEEE Transactions on Power Electronics
Volume27
Issue number3
DOIs
StatePublished - Feb 20 2012

Keywords

  • DC-DC converter
  • PID control formulation
  • derivative gain
  • geometric surface
  • noise injection

ASJC Scopus subject areas

  • Electrical and Electronic Engineering

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